pokerth: fix build error which was probably due to a changing C++ dependency (boost/g++?)

Ticks one box in #28643

pkgs/games/pokerth/default.nix

···
 
   outputs = [ "out" "server" ];
 
-  qmakeFlags = [ "pokerth.pro" ];
+  qmakeFlags = [ "pokerth.pro" "DEFINES+=_WEBSOCKETPP_NOEXCEPT_TOKEN_=noexcept" ];
 
   NIX_CFLAGS_COMPILE = [ "-I${SDL.dev}/include/SDL" ];